1,435 research outputs found
Extended Formulations in Mixed-integer Convex Programming
We present a unifying framework for generating extended formulations for the
polyhedral outer approximations used in algorithms for mixed-integer convex
programming (MICP). Extended formulations lead to fewer iterations of outer
approximation algorithms and generally faster solution times. First, we observe
that all MICP instances from the MINLPLIB2 benchmark library are conic
representable with standard symmetric and nonsymmetric cones. Conic
reformulations are shown to be effective extended formulations themselves
because they encode separability structure. For mixed-integer
conic-representable problems, we provide the first outer approximation
algorithm with finite-time convergence guarantees, opening a path for the use
of conic solvers for continuous relaxations. We then connect the popular
modeling framework of disciplined convex programming (DCP) to the existence of
extended formulations independent of conic representability. We present
evidence that our approach can yield significant gains in practice, with the
solution of a number of open instances from the MINLPLIB2 benchmark library.Comment: To be presented at IPCO 201
Are reviewers suggested by authors as good as those chosen by editors? Results of a rater-blinded, retrospective study
BACKGROUND: BioMed Central (BMC) requires authors to suggest four reviewers when making a submission. Editors searching for reviewers use these suggestions as a source. The review process of the medical journals in the BMC series is open – authors and reviewers know each other's identity – although reviewers can make confidential comments to the editor. Reviews are published alongside accepted articles so readers may see the reviewers' names and recommendations. Our objective was to compare the performance of author-nominated reviewers (ANR) with that of editor-chosen reviewers (ECR) in terms of review quality and recommendations about submissions in an online-only medical journal. METHODS: Pairs of reviews from 100 consecutive submissions to medical journals in the BMC series (with one author-nominated and one editor-chosen reviewer and a final decision) were assessed by two raters, blinded to reviewer type, using a validated review quality instrument (RQI) which rates 7 items on 5-point Likert scales. The raters discussed their ratings after the first 20 pairs (keeping reviewer type masked) and resolved major discrepancies in scoring and interpretation to improve inter-rater reliability. Reviewers' recommendations were also compared. RESULTS: Reviewer source had no impact on review quality (mean RQI score (± SD) 2.24 ± 0.55 for ANR, 2.34 ± 0.54 for ECR) or tone (mean scores on additional question 2.72 ANR vs 2.82 ECR) (maximum score = 5 in both cases). However author-nominated reviewers were significantly more likely to recommend acceptance (47 vs 35) and less likely to recommend rejection (10 vs 23) than editor-chosen reviewers after initial review (p < 0.001). However, by the final review stage (i.e. after authors had responded to reviewer comments) ANR and ECR recommendations were similar (65 vs 66 accept, 10 vs 14 reject, p = 0.47). The number of reviewers unable to decide about acceptance was similar in both groups at both review stages. CONCLUSION: Author-nominated reviewers produced reviews of similar quality to editor-chosen reviewers but were more likely to recommend acceptance during the initial stages of peer review
The diagnosis of colorectal cancer in patients with symptoms: finding a needle in a haystack
Patients often see primary care physicians with symptoms that might signal colorectal cancer but are also common in adults without cancer. Physicians and patients must then make a difficult decision about whether and how aggressively to evaluate the symptom. Favoring referral is that missed diagnoses lead to unnecessary testing, prolonged uncertainty, and continuing symptoms; also, the physician will suffer chagrin. It is not clear that diagnostic delay leads to progression to a more advanced stage. Against referral is that proper evaluation includes colonoscopy, with attendant inconvenience, discomfort, cost, and risk. The article by Hamilton et al, published this month in BMC Medicine, provides strong estimates of the predictive value of the various symptoms and signs of colorectal cancer and show how much higher predictive values are with increasing age and male sex. Unfortunately, their results also make clear that most colorectal cancers present with symptoms with low predictive values, < 1.2%. Models that include a set of predictive variables, that is, risk factors, age, sex, screening history, and symptoms, have been developed to guide primary prevention and clinical decision-making and are more powerful than individual symptoms and signs alone. Although screening for colorectal cancer is increasing in many countries, cancers will still be found outside screening programs so primary care physicians will remain at the front line in the difficult task of distinguishing everyday symptoms from life-threatening cancer
Intermediate behavior of Kerr tails
The numerical investigation of wave propagation in the asymptotic domain of
Kerr spacetime has only recently been possible thanks to the construction of
suitable hyperboloidal coordinates. The asymptotics revealed an apparent puzzle
in the decay rates of scalar fields: the late-time rates seemed to depend on
whether finite distance observers are in the strong field domain or far away
from the rotating black hole, an apparent phenomenon dubbed "splitting". We
discuss far-field "splitting" in the full field and near-horizon "splitting" in
certain projected modes using horizon-penetrating, hyperboloidal coordinates.
For either case we propose an explanation to the cause of the "splitting"
behavior, and we determine uniquely decay rates that previous studies found to
be ambiguous or immeasurable. The far-field "splitting" is explained by
competition between projected modes. The near-horizon "splitting" is due to
excitation of lower multipole modes that back excite the multipole mode for
which "splitting" is observed. In both cases "splitting" is an intermediate
effect, such that asymptotically in time strong field rates are valid at all
finite distances. At any finite time, however, there are three domains with
different decay rates whose boundaries move outwards during evolution. We then
propose a formula for the decay rate of tails that takes into account the
inter--mode excitation effect that we study.Comment: 16 page
Breastfeeding : a potential excretion route for mothers and implications for infant exposure to perfluoroalkyl acids
Background: The presence of perfluoroalkyl acids (PFAAs) in breast milk has been documented, but their lactational transfer has been rarely studied. Determination of the elimination rates of these chemicals during breastfeeding is important and critical for assessing exposure in mothers and infants.
Objectives: We aimed to investigate the association between breastfeeding and maternal serum concentrations of perfluorooctanoic acid (PFOA), perfluorooctane sulfonate (PFOS), perfluorononanoic acid (PFNA), and perfluorohexane sulfonate (PFHxS). For a subset of the population, for whom we also have their infants’ measurements, we investigated associations of breastfeeding with infant serum PFAA concentrations.
Methods: The present analysis included 633 women from the C8 Science Panel Study who had a child < 3.5 years of age and who provided blood samples and reported detailed information on breastfeeding at the time of survey. PFAA serum concentrations were available for all mothers and 8% (n = 49) of the infants. Maternal and infant serum concentrations were regressed on duration of breastfeeding.
Results: Each month of breastfeeding was associated with lower maternal serum concentrations of PFOA (–3%; 95% CI: –5, –2%), PFOS (–3%; 95% CI: –3, –2%), PFNA (–2%; 95% CI: –2, –1%), and PFHxS (–1%; 95% CI: –2, 0%). The infant PFOA and PFOS serum concentrations were 6% (95% CI: 1, 10%) and 4% (95% CI: 1, 7%) higher per month of breastfeeding.
Conclusions: Breast milk is the optimal food for infants, but is also a PFAA excretion route for lactating mothers and exposure route for nursing infants
Natural variation in immune responses to neonatal mycobacterium bovis bacillus calmette-guerin (BCG) vaccination in a cohort of Gambian infants
Background There is a need for new vaccines for tuberculosis (TB) that protect against adult pulmonary disease in regions where BCG is not effective. However, BCG could remain integral to TB control programmes because neonatal BCG protects against disseminated forms of childhood TB and many new vaccines rely on BCG to prime immunity or are recombinant strains of BCG. Interferon-gamma (IFN-) is required for immunity to mycobacteria and used as a marker of immunity when new vaccines are tested. Although BCG is widely given to neonates IFN- responses to BCG in this age group are poorly described. Characterisation of IFN- responses to BCG is required for interpretation of vaccine immunogenicity study data where BCG is part of the vaccination strategy. Methodology/Principal Findings 236 healthy Gambian babies were vaccinated with M. bovis BCG at birth. IFN-, interleukin (IL)-5 and IL-13 responses to purified protein derivative (PPD), killed Mycobacterium tuberculosis (KMTB), M. tuberculosis short term culture filtrate (STCF) and M. bovis BCG antigen 85 complex (Ag85) were measured in a whole blood assay two months after vaccination. Cytokine responses varied up to 10 log-fold within this population. The majority of infants (89-98% depending on the antigen) made IFN- responses and there was significant correlation between IFN- responses to the different mycobacterial antigens (Spearman’s coefficient ranged from 0.340 to 0.675, p=10-6-10-22). IL-13 and IL-5 responses were generally low and there were more non-responders (33-75%) for these cytokines. Nonetheless, significant correlations were observed for IL-13 and IL-5 responses to different mycobacterial antigens Conclusions/Significance Cytokine responses to mycobacterial antigens in BCG-vaccinated infants are heterogeneous and there is significant inter-individual variation. Further studies in large populations of infants are required to identify the factors that determine variation in IFN- responses
Unexpected depletion in plasma choline and phosphatidylcholine concentrations in a pregnant woman with bipolar affective disorder being treated with lithuim, haloperidol and benztropine: a case report
<p>Abstract</p> <p>Introduction</p> <p>Patients with bipolar affective disorder can be effectively managed with pharmacological intervention. This case report describes a pregnant woman with a ten-year history of bipolar affective disorder that was being treated with lithium, haloperidol and benztropine.</p> <p>Case presentation</p> <p>The patient had a normal pregnancy, but developed an elevated blood pressure and started to lose weight at 36 weeks of gestation. During pregnancy, plasma concentrations of choline and phosphatidylcholine are increased to meet the demands of the foetus. However, our findings in this case included depletion of plasma choline and phosphatidylcholine concentrations. Other unusual outcomes included low placental weight and low infant birth weight.</p> <p>Conclusion</p> <p>This report suggests that the pharmacological management of this patient could possibly account for the findings.</p
Saturn satellites as seen by Cassini Mission
In this paper we will summarize some of the most important results of the
Cassini mission concerning the satellites of Saturn. Given the long duration of
the mission, the complexity of the payload onboard the Cassini Orbiter and the
amount of data gathered on the satellites of Saturn, it would be impossible to
describe all the new discoveries made, therefore we will describe only some
selected, paramount examples showing how Cassini's data confirmed and extended
ground-based observations. In particular we will describe the achievements
obtained for the satellites Phoebe, Enceladus and Titan. We will also put these
examples in the perspective of the overall evolution of the system, stressing
out why the selected satellites are representative of the overall evolution of
the Saturn system.Comment: 34 pages, 10 figures, to appear on the special issue of Earth, Moon
and Planets for the Elba worksho
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